Methods and systems for PDCCH blind decoding in mobile communications

ABSTRACT

Various methods and systems for efficiently performing the blind decoding of downlink signals is described. Several forms of arranging possible CCE combinations are examined and investigated. Based on PDCCH size estimation/information, CCE concatenations that are most likely (of limited sets) can be arrived at. Tree-based concatenations are also devised using largest CCE ordering to align smaller CCE sizes to similar boundaries. By such ordering, the search space for all possible CCE ordering and sizes can be reduced to an efficient tree. Set mapping between possible lnposelstartCCElnposelend/REs are also described using a first set to secondary and tertiary sets. Various other ordering and sorting schemes are also detailed that enable a blind decode of a PDCCH channel to be efficiently performed.

CLAIM OF PRIORITY

The present Application for Patent is a continuation of patentapplication Ser. No. 12/259,798, entitled “Methods and Systems for PDCCHBlind Decoding in Mobile Communications” filed Oct. 28, 2008, nowallowed, which claims priority to Provisional Patent Application No.60/983,907, entitled “BDCCH Blind Decoding Methods and Systems,” filedOct. 30, 2007, both assigned to the assignee hereof and both herebyexpressly incorporated by reference herein.

FIELD

This disclosure relates generally to wireless communications, and moreparticularly to blind decoding of the Physical Downlink Control Channel(PDCCH) for user equipment.

BACKGROUND

For the purposes of the present document, the following abbreviationsapply:

AM Acknowledged Mode AMD Acknowledged Mode Data ARQ Automatic RepeatRequest BCCH Broadcast Control CHannel BCH Broadcast CHannel C- Control-CCCH Common Control CHannel CCH Control CHannel CCTrCH Coded CompositeTransport Channel CP Cyclic Prefix CRC Cyclic Redundancy Check CTCHCommon Traffic Channel D-BCH Dynamic Broadcast CHannel DCCH DedicatedControl CHannel DCH Dedicated CHannel DL DownLink DSCH Downlink SharedCHannel DTCH Dedicated Traffic CHannel FACH Forward link Access CHannelFDD Frequency Division Duplex Ll Layer 1 (physical layer) L2 Layer 2(data link layer) L3 Layer 3 (network layer) LI Length Indicator LSBLeast Significant Bit MAC Medium Access Control MBMS Multmedia BroadcastMulticast Service MCCH MBMS point-to-multipoint Control CHannel MRW MoveReceiving Window MSB Most Significant Bit MSCH MBMS point-to-multipointScheduling CHannel MTCH MBMS point-to-multipoint Traffic Channel P-BCHPrimary Broadcast CHannel PCCH Paging Control Channel PCFICH PhysicalControl Format Indicator CHannel PCH Paging Channel PDCCH PhysicalDownlink Control CHannel PDU Protocol Data Unit PHY PHYsical layer PHICHPhysical Hybrid-ARQ Indicator CHannel PhyCH Physical CHannels RACHRandom Access Channel RE Resource Element RS Reference Signal RLC RadioLink Control RoHC Robust Header Compression RRC Radio Resource ControlSAP Service Access Point SDU Service Data Unit SHCCH SHared channelControl CHannel SN Sequence Number SUFI SUper FIeld TCH Traffic CHannelTDD Time Division Duplex TFI Transport Format Indicator TM TransparentMode TMD Transparent Mode Data TTI Transmission Time Interval U- User-UE User Equipment UL UpLink UM Unacknowledged Mode UMD UnacknowledgedMode Data UMTS Universal Mobile Telecommunications System UTRA UMTSTerrestrial Radio Access UTRAN UMTS Terrestrial Radio Access Network

Universal Mobile Telecommunications System (UMTS) is one of thethird-generation (3G) wireless phone technologies. Currently, the mostcommon form of UMTS uses W-CDMA as the underlying air interface. UMTS isstandardized by the 3rd Generation Partnership Project (3GPP), and issometimes marketed as 3GSM as a way of emphasizing the combination ofthe 3G nature of the technology and the GSM standard which it wasdesigned to succeed.

UTRAN (UMTS Terrestrial Radio Access Network) is a collective term forthe Node-B's and Radio Network Controllers which make up the UMTS radioaccess network. The UTRAN allows connectivity between the UE and a corenetwork, and can include UEs, Node Bs, and Radio Network Controllers(RNCs)—noting that an RNC and Node B can be the same device, althoughtypical implementations have a separate RNC located in a central officeserving multiple Node B's.

For UMTS, a Broadcast Channel (BCH) may have a fixed pre-definedtransport format and may be broadcasted over the entire coverage area ofa cell. In Long Term Evolutino (LTE) which improves upon the UMTSstandard, the broadcast channel may be used to transmit a “SystemInformation field” necessary for system access. However, due to thelarge size of a System Information field, the BCH may be divided intotwo portions including a Primary Broadcast CHannel (P-BCH) and DynamicBroadcast CHannel (D-BCH). The P-BCH may contain basic Layer 1 (physicallayer)/Layer 2 (data link layer) (or “L1/L2”) system parameters usefulto demodulate the D-BCH, which in turn may contain the remaining SystemInformation field.

It may occur that a UE may need to blindly decode a Physical DownlinkControl Channel (PDCCH) from several possible formats and associatedControl Channel Elements (CCEs). Unfortunately, this may impose asubstantial burden on the UE that may exceed practical hardwarelimitations and thus lead to increased costs and/or reduced performanceof the UE.

Therefore, there is a need for addressing this issue. Accordingly,methods and systems for addressing this and other issues are disclosedherein.

SUMMARY

The foregoing needs are met, to a great extent, by the presentdisclosure.

In one of various aspects of the disclosure, a method to reduce theprocessing overhead for blind decoding a PDCCH signal is provided,comprising: estimating a suitable sized CCE segment in a PDCCH signal;generating a tree structure containing contiguous CCE aggregation levelsof the estimated CCE segment, wherein the CCE aggregations are multiplesof the estimated CCE segment; arranging the aggregation levels in ahierarchal order, wherein each level's initial position is coincidentwith all other levels' initial positions; and decoding the PDCCH signalby using boundaries defined by the tree structure, wherein theboundaries form a search path, enabling a reduced search for a blinddecode.

In one of various other aspects of the disclosure, a computer-readableproduct is provided, containing code for: estimating a suitable sizedCCE segment in a PDCCH signal; generating a tree structure containingcontiguous CCE aggregation levels of the estimated CCE segment, whereinthe CCE aggregations are multiples of the estimated CCE segment;arranging the aggregation levels in a hierarchal order, wherein eachlevel's initial position is coincident with all other levels' initialpositions; and decoding the PDCCH signal by using boundaries defined bythe tree structure, wherein the boundaries form a search path, enablinga reduced search for a blind decode.

In one of various aspects of the disclosure, an apparatus configured toreduce the processing overhead for PDCCH blind decoding is provided,comprising: circuitry configured to blind decode a PDCCH signal, thecircuitry capable of estimating a suitable sized CCE segment in a PDCCHsignal; capable of generating a tree structure containing contiguous CCEaggregation levels of the estimated CCE segment, wherein the CCEaggregations are multiples of the estimated CCE segment; capable ofarranging the aggregation levels in a hierarchal order, wherein eachlevel's initial position is coincident with all other levels' initialpositions; and capable of decoding the PDCCH signal by using boundariesdefined by the tree structure, wherein the boundaries form a searchpath, enabling a reduced search for a blind decode.

In one of various aspects of the disclosure, an apparatus to reduceprocessing overhead for PDCCH blind decoding is provided, comprising:means for estimating a suitable sized CCE segment in a PDCCH signal;means for generating a structure containing contiguous CCE aggregationlevels of the estimated CCE segment, wherein the CCE aggregations aremultiples of the estimated CCE segment; means for arranging theaggregation levels in a hierarchal order, wherein each level's initialposition is coincident with all other levels' initial positions; andmeans for decoding the PDCCH signal by using boundaries defined by thestructure, wherein the boundaries form a search path, enabling a reducedsearch for a blind decode.

In one of various aspects of the disclosure, a method to reduce theprocessing overhead for PDCCH blind decoding using an initial estimateof largest-to-smallest CCEs is provided comprising: estimating asuitable largest sized CCE segment in the PDCCH signal; sorting allcombinations of CCEs possible in the PDCCH into sets having a largestCCE in the beginning of its set, and smaller CCEs in the set are orderedin a largest-to-smallest order; ordering all the sorted sets into at agreatest number of elements to smallest number of elements order, orvice versus; and performing a reduced search space blind search usingelements from the ordered sets, starting with the set having thesmallest number of elements.

In one of various aspects of the disclosure, a computer-readable productis provided, containing instructions to reduce the processing overheadfor PDCCH blind decoding using an initial estimate oflargest-to-smallest CCEs, the instructions comprising: sorting allcombinations of CCEs possible in the PDCCH into sets having a largestCCE in the beginning of its set, and smaller CCEs in the set are orderedin a largest-to-smallest order; ordering all the sorted sets into at agreatest number of elements to smallest number of elements order, orvice versus; and performing a reduced search space blind search usingelements from the ordered sets, starting with the set having thesmallest number of elements.

In one of various aspects of the disclosure, an apparatus configured toreduce the processing overhead for PDCCH blind decoding using an initialestimate of largest-to-smallest CCEs is provided, comprising: circuitryconfigured to blind decode a PDCCH signal, wherein an initial estimateof the number of information bits of the PDCCH signal is based onsorting all combinations of CCEs possible in the PDCCH into sets havinga largest CCE in the beginning of its set, and smaller CCEs in the setare ordered in a largest-to-smallest order, the circuitry capable ofordering all the sorted sets into at least one of a greatest number ofelements to smallest number of elements order, or vice versus, and thecircuitry capable of performing a reduced search space blind searchusing elements from the ordered sets, starting with the set having thesmallest number of elements.

In one of various aspects of the disclosure, an apparatus configured toreduce the processing overhead for PDCCH blind decoding using an initialestimate of largest-to-smallest CCEs, comprising: means for sorting allcombinations of CCEs possible in the PDCCH into sets having a largestCCE in the beginning of its set, and smaller CCEs in the set are orderedin a largest-to-smallest order; means for ordering all the sorted setsinto at a greatest number of elements to smallest number of elementsorder, or vice versus; and means for performing a reduced search spaceblind search using elements from the ordered sets, starting with the sethaving the smallest number of elements.

In one of various aspects of the disclosure, a method to reduce theprocessing overhead for PDCCH blind decoding is provided, comprising:receiving a PDCCH signal; estimating a maximum number of informationbits used in the PDCCH signal; restraining a candidate number ofinformation bits to a first set of information bits; mapping a firstsubset of the first set to a second set that is not in the first set;mapping a second subset of the first set to a third set that is not inthe first set; restraining concatenation of elements of the sets to formlargest to smallest order; and performing a blind decoding initiallybased on elements in the first set, and proceeding to elements of thesecond set and third set.

In one of various aspects of the disclosure, a computer-readable productis provided containing code for: receiving a PDCCH signal; estimating amaximum number of information bits used in the PDCCH signal; restraininga candidate number of information bits to a first set of informationbits; mapping a first subset of the first set to a second set that isnot in the first set; applying a second subset of the first set to athird set that is not in the first set; restraining concatenation ofelements of the sets to form largest to smallest order; and performing ablind decoding initially based on elements in the first set, andproceeding to elements of the second set and third set.

In one of various aspects of the disclosure, an apparatus configured toreduce the processing overhead for PDCCH blind decoding is provided,comprising: means for receiving a PDCCH signal; means for estimating amaximum number of information bits used in the PDCCH signal; means forrestraining a candidate number of information bits to a first set ofinformation bits; means for mapping a first subset of the first set to asecond set that is not in the first set; means for mapping a secondsubset of the first set to a third set that is not in the first set;means for restraining concatenation of elements of the sets to formlargest to smallest order; and means for performing a blind decodinginitially based on elements in the first set, and proceeding to elementsof the second set and third set.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a multiple access wireless communicationsystem.

FIG. 2 is a block diagram of an embodiment of a transmitter system andreceiver system in a MIMO configuration.

FIG. 3 is an illustration of a multiple access wireless communicationsystem.

FIG. 4A-B are diagrams illustrating a PDCCH in a 1 ms subframe and CCEhierarchy, respectively.

FIGS. 5-8 depict graphical representations of the number of PDCCHs as afunction of different bandwidths, the span of the PDCCH, and a short CP.

FIG. 9 provides a graphical illustration of a contiguous and tree-basedconcatenation.

FIG. 10 contains a flowchart illustrating an exemplary process.

DETAILED DESCRIPTION

Various embodiments are now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of one or more embodiments. It may be evident, however,that such embodiment(s) may be practiced without these specific details.In other instances, well-known structures and devices are shown in blockdiagram form in order to facilitate describing one or more embodiments.

As used in this application, the terms “component,” “module,” “system,”and the like are intended to refer to a computer-related entity, eitherhardware, firmware, a combination of hardware and software, software, orsoftware in execution. For example, a component can be, but is notlimited to being, a process running on a processor, a processor, anobject, an executable, a thread of execution, a program, and/or acomputer. By way of illustration, both an application running on acomputing device and the computing device can be a component. One ormore components can reside within a process and/or thread of executionand a component can be localized on one computer and/or distributedbetween two or more computers. In addition, these components can executefrom various computer readable media having various data structuresstored thereon. The components can communicate by way of local and/orremote processes such as in accordance with a signal having one or moredata packets (e.g., data from one component interacting with anothercomponent in a local system, distributed system, and/or across a networksuch as the Internet with other systems by way of the signal).

Furthermore, various embodiments are described herein in connection withan access terminal. An access terminal can also be called a system,subscriber unit, subscriber station, mobile station, mobile, remotestation, remote terminal, mobile device, user terminal, terminal,wireless communication device, user agent, user device, or userequipment (UE). An access terminal can be a cellular telephone, acordless telephone, a Session Initiation Protocol (SIP) phone, awireless local loop (WLL) station, a personal digital assistant (PDA), ahandheld device having wireless connection capability, computing device,or other processing device connected to or utilizing a wireless modem.Moreover, various embodiments are described herein in connection with abase station. A base station can be utilized for communicating withaccess terminal(s) and can also be referred to as an access point, NodeB, eNode B (eNB), or some other terminology. Depending on the context ofthe descriptions provided below, the term Node B may be replaced witheNB and/or vice versus as according to the relevant communication systembeing employed.

An orthogonal frequency division multiplex (OFDM) communication systemeffectively partitions the overall system bandwidth into multiple(N_(F)) subcarriers, which may also be referred to as frequencysubchannels, tones, or frequency bins. For an OFDM system, the data tobe transmitted (i.e., the information bits) is first encoded with aparticular coding scheme to generate coded bits, and the coded bits arefurther grouped into multi-bit symbols that are then mapped tomodulation symbols. Each modulation symbol corresponds to a point in asignal constellation defined by a particular modulation scheme (e.g.,M-PSK or M-QAM) used for data transmission. At each time interval thatmay be dependent on the bandwidth of each frequency subcarrier, amodulation symbol may be transmitted on each of the N_(F) frequencysubcarrier. OFDM may be used to combat inter-symbol interference (ISI)caused by frequency selective fading, which is characterized bydifferent amounts of attenuation across the system bandwidth.

A multiple-input multiple-output (MIMO) communication system employsmultiple (N_(T)) transmit antennas and multiple (N_(R)) receive antennasfor data transmission. A MIMO channel formed by the N_(T) transmit andN_(R) receive antennas may be decomposed into N_(S) independentchannels, with N_(S)≦min{N_(T),N_(R)}. Each of the N_(S) independentchannels may also be referred to as a spatial subcarrier of the MIMOchannel and corresponds to a dimension. The MIMO system can provideimproved performance (e.g., increased transmission capacity) if theadditional dimensionalities created by the multiple transmit and receiveantennas are utilized.

For a MIMO system that employs OFDM (i.e., a MIMO-OFDM system), N_(F)frequency subcarriers are available on each of the N_(S) spatialsubchannels for data transmission. Each frequency subcarrier of eachspatial subchannel may be referred to as a transmission channel. Thereare N_(F)·N_(S) transmission channels thus available for datatransmission between the N_(T) transmit antennas and N_(R) receiveantennas.

For a MIMO-OFDM system, the N_(F) frequency subchannels of each spatialsubchannel may experience different channel conditions (e.g., differentfading and multipath effects) and may achieve differentsignal-to-noise-and-interference ratios (SNRs). Each transmittedmodulation symbol is affected by the response of the transmissionchannel via which the symbol was transmitted. Depending on the multipathprofile of the communication channel between the transmitter andreceiver, the frequency response may vary widely throughout the systembandwidth for each spatial subchannel, and may further vary widely amongthe spatial subchannels.

Referring to FIG. 1, a multiple access wireless communication systemaccording to one embodiment is illustrated. An access point 100 (AP)includes multiple antenna groups, one including 104 and 106, anotherincluding 108 and 110, and an additional including 112 and 114. In FIG.1, only two antennas are shown for each antenna group, however, more orfewer antennas may be utilized for each antenna group. Access terminal116 (AT) is in communication with antennas 112 and 114, where antennas112 and 114 transmit information to access terminal 116 over forwardlink 120 and receive information from access terminal 116 over reverselink 118. Access terminal 122 is in communication with antennas 106 and108, where antennas 106 and 108 transmit information to access terminal122 over forward link 126 and receive information from access terminal122 over reverse link 124. In a FDD system, communication links 118,120, 124 and 126 may use different frequency for communication. Forexample, forward link 120 may use a different frequency then that usedby reverse link 118.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the access point. In theembodiment, antenna groups each are designed to communicate to accessterminals in a sector, of the areas covered by access point 100.

In communication over forward links 120 and 126, the transmittingantennas of access point 100 utilize beamforming in order to improve thesignal-to-noise ratio of forward links for the different accessterminals 116 and 124. Also, an access point using beamforming totransmit to access terminals scattered randomly through its coveragecauses less interference to access terminals in neighboring cells thanan access point transmitting through a single antenna to all its accessterminals.

An access point may be a fixed station used for communicating with theterminals and may also be referred to as an access point, a Node B, orsome other terminology. An access terminal may also be called an accessterminal, user equipment (UE), a wireless communication device,terminal, access terminal or some other terminology.

FIG. 2 is a block diagram of an embodiment of a transmitter system 210(also known as the access point) and a receiver system 250 (also knownas access terminal) in a MIMO system 200. At the transmitter system 210,traffic data for a number of data streams is provided from a data source212 to transmit (TX) data processor 214.

In an embodiment, each data stream is transmitted over a respectivetransmit antenna. TX data processor 214 formats, codes, and interleavesthe traffic data for each data stream based on a particular codingscheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., BPSK, QSPK, M-PSK, or M-QAM)selected for that data stream to provide modulation symbols. The datarate, coding, and modulation for each data stream may be determined byinstructions performed by processor 230. Memory 232 may providesupporting memory services to processor 230.

The modulation symbols for all data streams are then provided to a TXMIMO processor 220, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulationsymbol streams to N_(T) transmitters (TMTR) 222 a through 222 t. Incertain embodiments, TX MIMO processor 220 applies beamforming weightsto the symbols of the data streams and to the antenna from which thesymbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transmitters 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are receivedby N_(R) antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective receiver (RCVR) 254 a through254 r. Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by RX data processor 260 is complementary to thatperformed by TX MIMO processor 220 and TX data processor 214 attransmitter system 210.

A processor 270 periodically determines which pre-coding matrix to use(discussed below). Processor 270 formulates a reverse link messagecomprising a matrix index portion and a rank value portion. Memory 262may provide supporting memory services to processor 270.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 238, whichalso receives traffic data for a number of data streams from a datasource 236, modulated by a modulator 280, conditioned by transmitters254 a through 254 r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240, and processed by a RX data processor242 to extract the reserve link message transmitted by the receiversystem 250. Processor 230 then determines which pre-coding matrix to usefor determining the beamforming weights and then processes the extractedmessage.

Referring to FIG. 3, a multiple access wireless communication system 300according to one aspect is illustrated. The multiple access wirelesscommunication system 300 includes multiple regions, including cells 302,304, and 306. In the aspect of FIG. 3, each cell 302, 304, and 306 mayinclude a Node B that includes multiple sectors. The multiple sectorscan be formed by groups of antennas with each antenna responsible forcommunication with UEs in a portion of the cell. For example, in cell302, antenna groups 312, 314, and 316 may each correspond to a differentsector. In cell 304, antenna groups 318, 320, and 322 each correspond toa different sector. In cell 306, antenna groups 324, 326, and 328 eachcorrespond to a different sector.

Each cell 302, 304 and 306 can include several wireless communicationdevices, e.g., User Equipment or UEs, which can be in communication withone or more sectors of each cell 302, 304 or 306. For example, UEs 330and 332 can be in communication with Node B 342, UEs 334 and 336 can bein communication with Node B 344, and UEs 338 and 340 can be incommunication with Node B 346.

Information and/or data is conveyed via channels. These channels may berepresented by physical hardware, frequencies, time bands, logicalconnections or abstract representations, and so forth, depending on thecontext and use thereof. In the UMTS framework, logical channels areclassified into Control Channels and Traffic Channels. Logical ControlChannels comprises Broadcast Control Channel (BCCH), which is DL channelfor broadcasting system control information. Paging Control Channel(PCCH), which is DL channel that transfers paging information. MulticastControl Channel (MCCH), which is Point-to-multipoint DL channel used fortransmitting Multimedia Broadcast and Multicast Service (MBMS)scheduling and control information for one or several MTCHs. Generally,after establishing RRC connection this channel is only used by UEs thatreceive MBMS (Note: old MCCH+MSCH). Dedicated Control Channel (DCCH) isPoint-to-point bi-directional channel that transmits dedicated controlinformation and used by UEs having an RRC connection. In one aspect,Logical Traffic Channels can comprise a Dedicated Traffic Channel(DTCH), which is a point-to-point bi-directional channel, dedicated toone UE, for the transfer of user information. Also, a Multicast TrafficChannel (MTCH) for Point-to-multipoint DL channel for transmittingtraffic data.

In an aspect, Transport Channels are classified into DL and UL. DLTransport Channels comprises a Broadcast Channel (BCH), Downlink SharedData Channel (DL-SDCH) and a Paging Channel (PCH), the PCH for supportof UE power saving (DRX cycle is indicated by the network to the UE),broadcasted over entire cell and mapped to PHY resources which can beused for other control/traffic channels. The UL Transport Channelscomprises a Random Access Channel (RACH), a Request Channel (REQCH), aUplink Shared Data Channel (UL-SDCH) and plurality of PHY channels. ThePHY channels comprise a set of DL channels and UL channels.

The DL PHY channels comprises:

-   -   Common Pilot Channel (CPICH)    -   Synchronization Channel (SCH)    -   Common Control Channel (CCCH)    -   Shared DL Control Channel (SDCCH)    -   Multicast Control Channel (MCCH)    -   Shared UL Assignment Channel (SUACH)    -   Acknowledgement Channel (ACKCH)    -   DL Physical Shared Data Channel (DL-PSDCH)    -   UL Power Control Channel (UPCCH)    -   Paging Indicator Channel (PICH)    -   Load Indicator Channel (LICH)

The UL PHY Channels comprises:

-   -   Physical Random Access Channel (PRACH)    -   Channel Quality Indicator Channel (CQICH)    -   Acknowledgement Channel (ACKCH)    -   Antenna Subset Indicator Channel (ASICH)    -   Shared Request Channel (SREQCH)    -   UL Physical Shared Data Channel (UL-PSDCH)    -   Broadband Pilot Channel (BPICH)

In an aspect, a channel structure is provided that preserves low PAR (atany given time, the channel is contiguous or uniformly spaced infrequency) properties of a single carrier waveform.

For UMTS, a Broadcast Channel (BCH) may have a fixed pre-definedtransport format and may be broadcasted over the entire coverage area ofa cell. In LTE, the broadcast channel may be used to transmit a “SystemInformation field” necessary for system access. However, due to thelarge size of the System Information field, the BCH may be divided intomultiple portions including a Primary Broadcast CHannel (P-BCH) andDynamic Broadcast CHannel (D-BCH). The P-BCH may contain basic Layer 1(physical layer)/Layer 2 (data link layer) (or “L1/L2”) systemparameters useful to demodulate the D-BCH, which in turn may contain theremaining System Information field.

An example of the multiple portioning of the BCH for a downlink pagingscenario is provided in FIG. 4A, where a PDCCH and PDSCH is shown in a 1ms subframe. FIG. 4A is instructive in illustrating that the fore of thesubframe contains resource elements (REs) 410 arranged in the timestrips 420. It is understood in the OFDM environment that the PDCCHstructure is based on CCEs which are built from REs 410. Depending onthe system, there are 36 REs per CCE with each RE 410 based on a tone ormodulation symbol. And each tone or modulation symbol corresponding to apair of bits. That is, each CCE consists of 36 REs which in turn consistof 2 bits or 2 coded values. Therefore, for each individual CCE there isan equivalent of 72 coded bits/values. The PDCCH may accommodatemultiple CCEs at different times, when the channel characteristicsbecome degraded in order to provide better information integrity.

FIG. 4B is a diagram illustrating CCEs and their bit relationship. Asapparent in FIG. 4B, the CCE combinations are in ascending pairs, i.e.,1, 2, 4, and 8. Thus, CCEs can be represented as the set of elements {1,2, 4, 8}, with the lowest element having 72 coded bits and the highestelement having 576 coded bits. As mentioned above, the PDCCH structureis formed by combinations of the CCEs. Thus, the PDCCH train may containvarious combinations of the set elements defined above. For example, aPDCCH train may contain the following CCE elements—1, 8, 8, 2, 4, 1, 8,etc. Combinatorially speaking, for a given size of CCEs (X), in anunrestricted or non-constrained arrangement there are (X 1)+(X 2)+(X4)+(X 8) total possible bit combinations. If the size of the CCE is 32,there will be 10,554,788 possible combination of bits in the PDDCH. Itshould be noted that though FIG. 4B illustrates a maximum CCE size of 8,in some embodiments, there may be more or even less CCEs, according todesign implementation.

It may occur that a UE may need to blindly decode a Physical DownlinkControl Channel (PDCCH) from several possible formats and associatedControl Channel Elements (CCEs). Unfortunately, this may impose asubstantial burden on the UE that may exceed practical hardwarelimitations and thus lead to increased costs and/or reduced performanceof the UE. In view of this, the following exemplary approaches arepresented to reducing the number of possible combinations by exploitingat least the limited pairing nature of the CCEs.

Studies are provided with a mind to understanding how the CCEs areconcatenated and how a “blind” search can be performed to reduce theeffort required to perform the blind decode.

One exemplary design solution may include limiting the number ofinformation bits per PDCCH to sets of different possible numbers. Fivesets being a suitable number of the possible numbers for the examplesprovided herein. Of course, more or less sets may be utilized accordingto design preference. Using five sets, as an example, the problem can bebroken down into two parts, including: (1) identifying those CCEsassociated with a PDCCH (decoupling the CCE associated with PHICH andPDCCH), and (2) blind decoding of the PDCCH within its associated CCE.

For the disclosed approach to PDCCH blind decoding, a number ofassumptions may be made, including: (1) a UE has decoded a particularP-BCH correctly, and (2) the decoded P-BCH contains information relevantfor CCE identification.

In the absence of PDCCH-less operation of a D-BCH, the relevant PDCCHCCE identification may be needed even for UEs acquiring a cell.Therefore one cannot assume any signaling on D-BCH. However, ifPDCCH-less operation of D-BCH is allowed, then relevant information canbe signaled on the related D-BCH.

Generally, for E-UTRA there can be three types of CCEs to consider:

Mini-CCEs,

PHICH CCEs and

PDCCH CCEs.

Mini-CCE can consist of 4 Resource elements (REs) noting that thedefinition might be changed to 2 REs in view of the PHICH structureoccurring in long Cyclic Prefix (CP) scenarios. Mini-CCEs may be used as“building blocks” for PCFICHs, PDCCHs and PHICHs.

PHICH CCEs can consist of 12 REs noting that a short CP may includethree strips of 4 RE each and a long CP may include 6 strips of 2 REseach. Note that, among the various LTE downlink control channels, thePHICH can be used to transmit ACK/NACK for uplink transmission.

A PHICH has a hybrid CDM-FDM structure. Hybrid CDM/FDM signals allowsfor power control between acknowledgments for different users andprovides good interference averaging. In addition, it can also providefrequency diversity for different users. Thus, the Bandwidth and powerload for a PHICH doesn't have to be balanced, and to identify the CCEfor a PDCCH, one may able to do so by considering only the bandwidthload.

PDCCH CCEs may have four types of REs. In this example, those four typesmay consist of {36, 72, 144, 288} REs, respectively.

Based on the above, let N denote the number of Physical uplink sharedchannels (PUSCHs) to be acknowledged in downlink. Since there may be3-bits to signal a cyclic shift for Spatial Division Multiple Access(SDMA), the theoretical maximum value of N equals 8× number of physicalresource block (PRB) pairs in uplink. (2³=8).

In an effort to count how many CCEs are available for PDCCH(assignments), various resources can be discounted which are used forother control information. The other control information can be the DLACKs (PHICH) and the PCFICH (Physical Control Format Indicator Channel).The relevance of this is to see how many net CCEs are available in thePDCCH, and based on constraints provided in that information tailor theblind decode accordingly.

Beginning with the definitions Nmax_prb_bw=the number of resource blocksfor PUSCH transmission; and f_PHICH=the fractional use of PHICHresources (Physical HARQ Indicator Channel), let Nmax_bw_rx indicate themaximum number of PUSCHs to be acknowledged for a given bandwidth andnumber of Rx antennas (Nrx), thenNmax_(—) bw _(—) rx=min(Nrx,8)*Nmax_(—) prb _(—) bw; and  Eq (1)N≦Nmax_(—) bw _(—) rx  Eq (2)

Design Approach: First note that a PHICH bandwidth load can be indicatedin the respective PBCH. There may be 2-bits to indicate the fractionalload as a function of Nmax_bw_rx so that the fractional load f_phich={1,½, ¼, ⅛}.

The Number of REs reserved for a PHICH (Nphich_re) is an importantconsideration to determine, and may be calculated, depending on CP, by:Nphich_(—) re(short CP)=12*ceil(f_phich*Nmax_(—) bw _(—) rx/4)  Eq (3)Nphich_(—) re(long CP)=12*ceil(f_phich*Nmax_(—) bw _(—) rx/2)  Eq (4)

Note that the number of REs reserved for a PHICH needs to be consistentwith the value of n indicated in the respective PCFICH. In practice, aneNB may benefit by taking this into account.

For example, for frequency=5 MHz, Nrx=4, for short CP

then Nmax_bw_rx=100, the resultant f_phich=1. Therefore, using the aboveequations, the resultant Nphich_re (short CP)=300. When the number ofOFDM symbols (n) in the PDCCH=1

then Nphich_re (number of REs available in 1st symbol)=200 which is<Nphich_re (short CP). Consequently, a significant reduction in thesearch possibilities is obtained.

Note that n is the number of OFDM symbols in the PDCCH spans, and forthe present embodiments may equal 1, 2 or 3. Accordingly, the number ofREs reserved for a PHICH (Nphich)_re can change based on differentfactors.

Tables 1-5 below further outline the results for Nphich_re for a varietyof conditions for different CPs and different loads.

TABLE 1 Short CP − Load = 0.125 Load Nphich_re (Number Bandwidth Numberof Rx Nmax_bw_rx of ACKs) 1.4 MHz  2  14 0.125 12 (4)   5 MHz 2  500.125 24 (8)  10 MHz 2 100 0.125 48 (16) 20 MHz 2 200 0.125 84 (28)

TABLE 2 Short CP − Load = 0.25 Nphich_re (Number Bandwidth Number of RxNmax_bw_rx Load of ACKs) 1.4 MHz   2  14 0.25 12 (4)   5 MHz 2  50 0.2548 (16) 10 MHz 2 100 0.25 84 (28) 20 MHz 2 200 0.25 156 (52) 

TABLE 3 Short CP − Load = 0.50 Nphich_re (Number Bandwidth Number of RxNmax_bw_rx Load of ACKs) 1.4 MHz  2  14 0.5 24 (8)   5 MHz 2  50 0.5 84(28) 10 MHz 2 100 0.5 156 (52)  20 MHz 2 200 0.5 300 (100)

TABLE 4 Long CP − Load = 0.125 Nphich_re (Number Bandwidth Number of RxNmax_bw_rx Load of ACKs) 1.4 MHz  2  14 0.125 12 (2)   5 MHz 2  50 0.12548 (8)  10 MHz 2 100 0.125 84 (14) 20 MHz 2 200 0.125 156 (26) 

TABLE 5 Long CP − Load = 0.25 Nphich_re Bandwidth Number of RxNmax_bw_rx Load (Number of ACKs) 1.4 MHz  2  14 0.25 24 (4)   5 MHz 2 50 0.25 84 (14) 10 MHz 2 100 0.25 156 (26)  20 MHz 2 200 0.25 300 (50) 

Next, consider PHICH CCE to RE mapping. Such can be mapped “around” anRE for a given RS even if there is only one Tx antenna. Thissubstantially simplifies the mapping. Given the following definitions:

-   -   N_re=number of resource elements    -   Nrs_re: number of resource elements for RS (reference signal)    -   Npcfich_re: number of resource elements for PCFICH (Physical        Control Format Indicator Channel)

Interleaver mapping can be fixed as a function of Nphich_re and theNumber of Tx antennas. In the following example, the net number ofresources available for PDCCH (assignments) transmission is calculated,while discounting the tones (REs) that are use for other tasks (withinthe control region). The remaining REs can then be made available forPDCCH, and for the purpose of this disclosure can be denoted asNpdcch_re, which may be calculated by:Npdcch_(—) re=36*floor((Navail_(—) re−Npcfich_(—) re−Nphich_(—)re)/36)  Eq (5)and the number of available REs calculated by:Navail_(—) re=N _(—) re−Nrs _(—) re  Eq (6)

Tables 6 and 7 below are provided to demonstrate the number of Npdcch_refor short CPs and a number of different PHISH loads.

TABLE 6 Short CP − PHICH Load = 0.125 Nphich_re Npdcch_re BandwidthNumber of Tx n (Number of ACKs) (Number of Grants) 1.4 MHz  {1, 2} 1 12(4)   0 (0)  5 MHz {1, 2} 1 24 (8)  144 (4) 10 MHz {1, 2} 1 48 (16) 324(9) 20 MHz {1, 2} 1 84 (28)  684 (19)

TABLE 7 Short CP − PHICH Load = 0.125 Nphich_re Npdcch_re BandwidthNumber of Tx n (Number of ACKs) (Number of Grants) 1.4 MHz  {1, 2} 3 12(4)  180 (5)   5 MHz {1, 2} 3 24 (8)  756 (21) 10 MHz {1, 2} 3 48 (16)1512 (42)  20 MHz {1, 2} 3 84 (28) 3096 (86) 

Continuing, FIGS. 5-8 depict graphical representations of the number ofPDCCHs as a function of acknowledgments for different bandwidths, thespan of the PDCCH, and assuming a short CP. Here we can see that thePDCCH size (short/long) affects the choice of CCEs. For example, a givenPDCCH size (1) can translate to a CCE set {1,2}, and a given PDCCH size(2) can translate to a CCE set {4,8}. Therefore, in one exemplaryembodiment, the PDCCH size operates as a metric in determining theconcatenation set. With this information, the number of combinations ofCCE sizes that the UE must search to blind decode can be reduced byexamining the type of PDCCH (size) being transmitted.

For PDCCH blind decoding, the number of PDCCH formats may depends on thefinal number of information bits. Assuming embodiments that have up to 5formats, with number of information bits ranging from 30 to 60, thepotential number of PDCCHs (based on 36 REs) may be calculated as:Npdcch_max=floor(Npdcch_(—) re/36)  Eq (7)

In practice, it should be appreciated that the number of blind decodescan increase drastically with Npdcch_max. For example, for Npdcch_max=3,there may be {1,1,1}, {2,1}, {1,2}

25 blind decodes, while for Npdcch_max=4, there may be {1,1,1,1},{2,1,1}, {1,2,1}, {1,1,2}, {2,2}, {4}

40 blind decodes, and for Npdcch_max=5 there may be {1,1,1,1,1},{2,1,1,1}, {1,2,1,1}, {1,1,2,1}, {1,1,1,2}, {1,4}, {4,1}

55 blind decodes.

Given such, it may be unreasonable to expect a given UE to monitor allpossible PDCCHs. However, several observations can be made to reduce thenumber of possibilities.

For a native code rate of Tailbiting Convolutional Code (TBCC)=⅓ andwhere the number of information bits=30-60 and where there is no codinggain beyond 144 RE for all formats, one may restrict the number of REsto {36, 72, 144}.

Where there is no coding gain beyond 72 RE for less than 48 informationbits, one may restrict the number of information bits=30-60 and REs to{36, 72}.

Noting that the code rate may be too high if 36 REs are used for morethan 48 information bits, may restrict the number of informationbits=48-60 and REs to {72, 144}. Therefore, using the above constraintseither individually or in combination, and where applicable, asignificant reduction in the number of REs or combinations can beachieved.

A further reduction in number of combinations can be achieved using anumber of approaches, e.g., by assuring that the concatenation of REsare always done in the beginning, rather than at any arbitrary location.For example, for an Npdcch_max=4 will provide {1,1,1,1}, {2,1,1}, {2,2},{4}, and the Npdcch_max=5 will result in {1,1,1,1,1}, {2,1,1,1},{2,2,1}, {4,1}.

The above sets illustrate an example where the first “pairs” ofidentical elements are collapsed. For example, for the Npdcch_max=4case, the first two is of the set {1,1,1,1} are collapsed into the first2 of the following set {2,1,1}; and the following two 1s of the set{2,1,1} is collapsed into the second 2 of the following set {2,2}; andthe first two 2s of the set {2,2} is collapsed into the set {4}. Thisapproach, of course, can be also applied to the Npdcch_max=5 case, aswell as for other Npdcch_max values. This arrangement can be considereda tree-based approach where the boundaries of the CCEs are continuousand “stacked.”

FIG. 9 provides a graphical illustration 900 of a contiguous andtree-based concatenation as described above using 16 CCEs, as anexample. In this example, the largest grouping is 8 CCEs 905, arrangedto form contiguous segments. The next grouping is formed of sets of 4CCEs 915 arranged continuous to each other, and in a “tree” above thepair of 8 CCE 905 segments where boundaries 920 for the pair of 4 CCEs915 alternately match up to the boundaries 910 of the 8 CCE 905segments. Similarly, the 2 CCEs 925 segments are contiguous to eachother and boundaries 930 alternately match up to the boundaries 920 forthe 4 CCE 915 segments. The boundaries 940 for the 1 CCE 935 segmentsare similarly “tree'd” to the larger lower CCE segment.

By having the CCEs contiguous and tree'd, the search algorithm can besimplified. For example, if a maximum of 4 CCEs 915 are understood to beused in the PDCCH, then using the restriction that the concatenation iscontiguous and tree-based, the search algorithm can be simplified tocoincide with the boundaries 920 (and 910—as it also falls on the sameboundary) of the 4 CCEs 915. If a maximum of 2 CCEs 925 are understoodto be used in the PDCCH, then the search can be simplified to theboundaries 930 of the 2 CCEs 925. Obviously, if the CCE size is known orestimated, it eliminates the need to search or decode on the non-CCEsize boundaries.

Also, it should be noted that with the above arrangement, the boundaryfor a given CCE coincides with a boundary of all the smaller CCEsegments. This provides a significant advantage. For example, boundary910 for the 8 CCE 905 matches up with a boundary for each of the 4 CCE915, 2 CCE 925, and 1 CCE 935. Similarly, the same can be said for the 4CCE 915 and all smaller CCEs above it. Therefore, each larger sizedCCEs' boundary also forms at least one boundary with all the smallersized CCE's. Thus, by starting on a gross, or large boundary, anysmaller CCE sizes also on that boundary can also be captured in thesearch.

As is apparent with contiguous/tree-based grouping, various methods forsearching or sorting may applied that are known in the art to accelerateor reduce the number of possible searches, including having the order ina root form, rather than a tree form.

In another embodiment of this disclosure, let the candidate number ofinformation bits be {32, 40, 48, 56, 64} where {32, 40, 48} bits map to{36, 72} RE and {56, 64} bits map to {72, 144} RE.

Assuming an Npdcch_max=4

the ordering of the REs become {1,1,1,1}, {2,1,1}, {2,2}, {4}, and thenumber of blind decodes=(4×3)+(2×5)+(1×2)=24 blind decodes, whichamounts to a 40% reduction in number of blind decodes.

Assuming an Npdcch_max=5

{1,1,1,1,1}, {2,1,1,1}, {2,2,1}, {4,1}, and the number of blinddecodes=(5×3)+(2×5)+(1×2)=27 blind decodes, which amounts to a 51%reduction in number of blind decodes.

Assuming an Npdcch_max=6

{1,1,1,1,1,1}, {2,1,1,1,1}, {2,2,1,1}, {2,2,2}, {4,1,1}, {4,2}, then thenumber of blind decodes=(6×3)+(3×5)+(1×2)=27 blind decodes. Note thatthis amounts to no change from the case where Npdcch_max=5.

Continuing, assuming an Npdcch_max=8, the number of blinddecodes=(8×3)+(4×5)+(2×2)=48 blind decodes.

A summary of one possible implementation is detailed below.

STEP 1: Restrain the candidate number of information bits to {32, 40,48, 56, 64} where by {32, 40, 48} bits map to {36, 72} RE, and {56, 64}bits map to {72, 144} RE.

STEP 2: Restrain RE concatenation such that it is always done in thebeginning, rather than at any arbitrary location, e.g, {a, b, c, . . . }such that a≧b≧c≧ . . . .

STEP 3: Restrain the number of PDCCHs monitored by a given UE to 8 orless.

For further optimization, the usage of 36 REs may be restricted to theminimum payload only, i.e., {32} bits mapping to {36, 72} RE, {40, 48}bits mapping to {72} RE, and {56, 64} bits mapping to {72, 144} RE. Forexample, assuming that Npdcch_max=8, the resulting number of blinddecodes=(8×1)+(4×5)+(2×2)=32 blind decodes.

FIG. 10 contains a flowchart 1000 illustrating an exemplary processbased on the above descriptions. The exemplary process, afterinitialization 1010, constrains the candidate numbers to a finite set asshown in step 1020. The finite set, for explanatory purposes, may becomprised of {32, 40, 48, 56, 64}, for example. Of the finite set, instep 1020, various combinations of the elements (i.e., subsets) will mapto another set of numbers that may not be a member of the finite set.For example, the subset {32, 40, 48} may be mapped to the “outside” set{36, 72} and the remaining subset {56, 64} may be mapped to the“outside” set {72, 144}. After step 1020, the exemplary process proceedsto step 1030 where it restrains RE concatenation to apreliminary/beginning process, rather than at an arbitrary location. Bythis method, an ordering can be imposed on the values.

Next, the exemplary process proceeds to step 1040 where the number ofPDCCHs monitored by a given UE is restrained, for example, to 8 or less.The exemplary process then terminates 1050.

The techniques described herein may be implemented by various means. Forexample, these techniques may be implemented in hardware, software, or acombination thereof. For a hardware implementation, the processing unitsused for channel estimation may be implemented within one or moreapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,other electronic units designed to perform the functions describedherein, or a combination thereof. With software, implementation can bethrough modules (e.g., procedures, functions, and so on) that performthe functions described herein. The software codes may be stored inmemory unit and executed by the processors.

Moreover, various aspects or features described herein can beimplemented as a method, apparatus, or article of manufacture usingstandard programming and/or engineering techniques. The term “article ofmanufacture” as used herein is intended to encompass a computer programaccessible from any computer-readable product, device, carrier, ormedia. For example, computer-readable product can include but are notlimited to magnetic storage devices (e.g., hard disk, floppy disk,magnetic strips, etc.), optical disks (e.g., compact disk (CD), digitalversatile disk (DVD), etc.), smart cards, and memory devices (e.g.,EPROM, card, stick, key drive, etc.). Additionally, various storagemedia described herein can represent one or more devices and/or othermachine-readable media for storing information. The term“machine-readable medium” can include, without being limited to,wireless channels and various other media capable of storing,containing, and/or carrying instruction(s) and/or data.

What has been described above includes examples of one or moreembodiments. It is, of course, not possible to describe everyconceivable combination of components or methodologies for purposes ofdescribing the aforementioned embodiments, but one of ordinary skill inthe art may recognize that many further combinations and permutations ofvarious embodiments are possible. Accordingly, the described embodimentsare intended to embrace all such alterations, modifications andvariations that fall within the spirit and scope of the appended claims.Furthermore, to the extent that the term “includes” is used in eitherthe detailed description or the claims, such term is intended to beinclusive in a manner similar to the term “comprising” as “comprising”is interpreted when employed as a transitional word in a claim.

What is claimed is:
 1. A method to reduce the processing overhead forblind decoding a physical downlink control channel (PDCCH) signal,comprising: identifying a control channel element (CCE) in the physicaldownlink control channel (PDCCH) signal; generating a set of CCEaggregations, wherein each CCE aggregation in the set of CCEaggregations comprises a multiple of the control channel element (CCE)configured in a contiguous block; arranging the set of CCE aggregationsin a hierarchical tree, wherein an initial CCE for each CCE aggregationlies at a common position in the hierarchical tree; and initiating thedecoding of the physical downlink control channel (PDCCH) signal at thecommon position of the CCE aggregations, enabling a reduced search for ablind decoding of the physical downlink control channel (PDCCH) signal.2. The method of claim 1, wherein each CCE aggregation comprises an evenmultiple of the control channel element (CCE).
 3. The method of claim 1,wherein each CCE aggregation comprises a reciprocal of an even multipleof the control channel element (CCE).
 4. The method of claim 1, whereinthe initiating the decoding comprises initiating the decoding of thephysical downlink control channel (PDCCH) signal at an initial CCE for alargest CCE aggregation in the set of CCE aggregations.
 5. The method ofclaim 4, wherein the set of CCE aggregations is arranged in thehierarchical tree starting with the largest CCE aggregation.
 6. Themethod of claim 5, wherein the set of CCE aggregations is arranged inthe hierarchical tree in size order from the largest CCE aggregation toa smallest CCE aggregation.
 7. The method of claim 1, wherein thecontrol channel element (CCE) comprises a set of resource elements(REs).
 8. The method of claim 1, wherein the decoding is performed byuser equipment (UE).
 9. The method of claim 8, wherein the userequipment (UE) comprises a cellular communications device.
 10. Themethod of claim 9, wherein the cellular communications device monitors aplurality of physical downlink control channel (PDCCH) signals.
 11. Themethod of claim 10, wherein further comprising constraining theplurality of physical downlink control channel (PDCCH) signals to amaximum number of signals.
 12. The method of claim 11, wherein themaximum number of signals is eight.
 13. The method of claim 1, furthercomprising constraining the bit sizes of resource elements (RE) in theset of resource elements (REs) to a set of discrete possible bit sizes.14. The method of claim 13, wherein the set of discrete possible bitsizes comprises a maximum of eight discrete possible bit sizes.
 15. Anon-transitory computer-readable product containing code executable by aprocessor for: identifying a control channel element (CCE) in a physicaldownlink control channel (PDCCH) signal; generating a set of CCEaggregations, wherein each CCE aggregation in the set of CCEaggregations comprises a multiple of the control channel element (CCE)configured in a contiguous block; arranging the set of CCE aggregationsin a hierarchical tree, wherein an initial CCE for each CCE aggregationlies at a common position in the hierarchical tree; and initiating thedecoding of the physical downlink control channel (PDCCH) signal at thecommon position of the CCE aggregations, enabling a reduced search for ablind decoding of the physical downlink control channel (PDCCH) signal.16. The computer-readable product of claim 15, wherein each CCEaggregation comprises an even multiple of the control channel element(CCE).
 17. The computer-readable product of claim 15, wherein each CCEaggregation comprises a reciprocal of an even multiple of the controlchannel element (CCE).
 18. The computer-readable product of claim 15,wherein the initiating the decoding comprises initiating the decoding ofthe physical downlink control channel (PDCCH) signal at an initial CCEfor a largest CCE aggregation in the set of CCE aggregations.
 19. Thecomputer-readable product of claim 18, wherein the set of CCEaggregations is arranged in the hierarchical tree starting with thelargest CCE aggregation.
 20. The computer-readable product of claim 19,wherein the set of CCE aggregations is arranged in the hierarchical treein size order from the largest CCE aggregation to a smallest CCEaggregation.
 21. The computer-readable product of claim 15, wherein thecontrol channel element (CCE) comprises a set of resource elements(REs).
 22. The computer-readable product of claim 15, wherein thedecoding is performed by user equipment (UE).
 23. The computer-readableproduct of claim 22, wherein the user equipment (UE) comprises acellular communications device.
 24. The computer-readable product ofclaim 23, wherein the cellular communications device monitors aplurality of physical downlink control channel (PDCCH) signals.
 25. Thecomputer-readable product of claim 24, wherein the code furthercomprises constraining the plurality of physical downlink controlchannel (PDCCH) signals to a maximum number of signals.
 26. Thecomputer-readable product of claim 25, wherein the maximum number ofsignals is eight.
 27. The computer-readable product of claim 15 whereinthe code further comprises constraining the bit sizes of resourceelements (RE) in the set of resource elements (REs) to a set of discretepossible bit sizes.
 28. The computer-readable product of claim 27,wherein the set of discrete possible bit sizes comprises a maximum ofeight discrete possible bit sizes.
 29. An apparatus configured to reducethe processing overhead for blind decoding a physical downlink controlchannel (PDCCH) signal, comprising: circuitry configured to identify acontrol channel element (CCE) in the physical downlink control channel(PDCCH) signal; circuitry configured to generate a set of CCEaggregations, wherein each CCE aggregation in the set of CCEaggregations comprises a multiple of the control channel element (CCE)configured in a contiguous block; circuitry configured to arrange theset of CCE aggregations in a hierarchical tree, wherein an initial CCEfor each CCE aggregation lies at a common position in the hierarchicaltree; and circuitry configured to initiate the decoding of the physicaldownlink control channel (PDCCH) signal at the common position of theCCE aggregations, enabling a reduced search for a blind decoding of thephysical downlink control channel (PDCCH) signal.
 30. The apparatus ofclaim 29, wherein each CCE aggregation comprises an even multiple of thecontrol channel element (CCE).
 31. The apparatus of claim 29, whereineach CCE aggregation comprises a reciprocal of an even multiple of thecontrol channel element (CCE).
 32. The apparatus of claim 29, whereinthe initiating the decoding comprises initiating the decoding of thephysical downlink control channel (PDCCH) signal at an initial CCE for alargest CCE aggregation in the set of CCE aggregations.
 33. Theapparatus of claim 32, wherein the set of CCE aggregations is arrangedin the hierarchical tree starting with the largest CCE aggregation. 34.The apparatus of claim 33, wherein the set of CCE aggregations isarranged in the hierarchical tree in size order from the largest CCEaggregation to a smallest CCE aggregation.
 35. The apparatus of claim29, wherein the control channel element (CCE) comprises a set ofresource elements (REs).
 36. The apparatus of claim 29, wherein theapparatus comprises user equipment (UE).
 37. The apparatus of claim 36,wherein the user equipment (UE) comprises a cellular communicationsdevice.
 38. The apparatus of claim 37, wherein the cellularcommunications device monitors a plurality of physical downlink controlchannel (PDCCH) signals.
 39. The apparatus of claim 38, wherein furthercomprising circuitry configured to constrain the plurality of physicaldownlink control channel (PDCCH) signals to a maximum number of signals.40. The apparatus of claim 39, wherein the maximum number of signals iseight.
 41. The apparatus of claim 29, further comprising circuitryconfigured to constrain the bit sizes of resource elements (RE) in theset of resource elements (REs) to a set of discrete possible bit sizes.42. The apparatus of claim 41, wherein the set of discrete possible bitsizes comprises a maximum of eight discrete possible bit sizes.
 43. Anapparatus configured to reduce the processing overhead for blinddecoding a physical downlink control channel (PDCCH) signal, comprising:means for identifying a control channel element (CCE) in the physicaldownlink control channel (PDCCH) signal; means for generating a set ofCCE aggregations, wherein each CCE aggregation in the set of CCEaggregations comprises a multiple of the control channel element (CCE)configured in a contiguous block; means for arranging the set of CCEaggregations in a hierarchical tree, wherein an initial CCE for each CCEaggregation lies at a common position in the hierarchical tree; andmeans for initiating the decoding of the physical downlink controlchannel (PDCCH) signal at the common position of the CCE aggregations,enabling a reduced search for a blind decoding of the physical downlinkcontrol channel (PDCCH) signal.
 44. The apparatus of claim 43, whereineach CCE aggregation comprises an even multiple of the control channelelement (CCE).
 45. The apparatus of claim 43, wherein each CCEaggregation comprises a reciprocal of an even multiple of the controlchannel element (CCE).
 46. The apparatus of claim 43, wherein theinitiating the decoding comprises initiating the decoding of thephysical downlink control channel (PDCCH) signal at an initial CCE for alargest CCE aggregation in the set of CCE aggregations.
 47. Theapparatus of claim 46, wherein the set of CCE aggregations is arrangedin the hierarchical tree starting with the largest CCE aggregation. 48.The apparatus of claim 47, wherein the set of CCE aggregations isarranged in the hierarchical tree in size order from the largest CCEaggregation to a smallest CCE aggregation.
 49. The apparatus of claim43, wherein the control channel element (CCE) comprises a set ofresource elements (REs).
 50. The apparatus of claim 43, wherein theapparatus comprises user equipment (UE).
 51. The apparatus of claim 50,wherein the user equipment (UE) comprises a cellular communicationsdevice.
 52. The apparatus of claim 51, wherein the cellularcommunications device monitors a plurality of physical downlink controlchannel (PDCCH) signals.
 53. The apparatus of claim 52, wherein furthercomprising means for constraining the plurality of physical downlinkcontrol channel (PDCCH) signals to a maximum number of signals.
 54. Theapparatus of claim 53, wherein the maximum number of signals is eight.55. The apparatus of claim 43, further comprising means for constrainingthe bit sizes of resource elements (RE) in the set of resource elements(REs) to a set of discrete possible bit sizes.
 56. The apparatus ofclaim 55, wherein the set of discrete possible bit sizes comprises amaximum of eight discrete possible bit sizes.